The main components of a drivetrain of a motor vehicle are a drive aggregate and a transmission. The transmission converts rotation speeds and torques, and thereby determines the traction force provided by the drive aggregate and supplies it to a drive output of the drivetrain. The present invention concerns a method for operating a drivetrain which has as its drive aggregate a hybrid drive with an internal combustion engine and an electric machine.
From the prior art it is known that a drivetrain of a motor vehicle, in particular a drivetrain of a utility vehicle, comprises a pressure reservoir system with at least one pressure reservoir and at least one pressure generator such as a compressor for filling one or more of the pressure reservoir(s). In utility vehicles, for example, compressed air stored in pressure reservoir systems is released when a brake pedal is actuated to apply a braking torque at the drive output of the drivetrain. When compressed air is drawn from the pressure reservoir system, this reduces the pressure in the pressure reservoir system.
In drivetrains known in practice, which have a hybrid drive as drive aggregate and also a pressure reservoir system, the one or more pressure generators of the pressure reservoir system is powered by the internal combustion engine, namely in such manner that even during purely electric driving the internal combustion engine is also idling in order to drive the one or more pressure generators of the pressure reservoir system and so to maintain sufficient pressure in the pressure reservoir system.
This is disadvantageous from the standpoints of both unnecessarily high fuel consumption and increased production of emissions and noise.